One objective of the proposed research is to understand the structure and biosynthesis of normal and tumor-associated surface antigens in order to determine how the surface of tumor cells differs from their normal counterparts and to understand the biochemical effects of the genetic mechanisms by which these changes arise. The second objective is to contribute to an understanding of how the immune system regulates tumor growth by identifying lymphocyte subpopulations with different cell surface properties and determining their functions. Both aims will be approached by continuation of previous studies of murine lymphocyte-specific surface antigens expressed on T lymphocytes and their tumors. The biosynthesis and expression of two of these T lymphocyte-specific surface glycoproteins (T200 and T25) will be studied biochemically as model normal cell surface antigens expressed on tumor cells. The regulation of expression of tumor-associated antigens will also be investigated as part of a collaborative program in which both biochemical and genetic methodology will be used. The isolation and characterization of T lymphocyte-specific surface antigens (T35 and T200) will continue. Monospecific antisera against the purified antigens will be prepared and used to determine the biological functions of the molecules themselves and the cells upon which they are expressed.